JP6641661B1 - Cutting tools - Google Patents

Abstract

A cutting tool comprising a base having a rake face and a coating covering the rake face, wherein the coating includes an α-Al2O3 layer provided on the base, and the α-Al2O3 layer includes α-Al2O3 crystal grains. The α-Al 2 O 3 layer has an area ratio of (001) -oriented crystal grains in the rake face of 50% to 90%, and in the residual stress measurement by the 2θ-sin 2ψ method using X-rays, The residual stress AA in the film obtained based on the crystal plane spacing of the (001) plane of the -Al2O3 layer is not less than -1000 MPa and less than 0 MPa. A cutting tool that has a residual stress BA in the film determined based on -1000 MPa or more and less than 0 MPa and satisfies the relational expression of | AA | ≦ | BA |.

Description

  The present disclosure relates to cutting tools. This application claims the priority based on Japanese Patent Application No. 2018-194133 filed on October 15, 2018. The entire contents described in the Japanese patent application are incorporated herein by reference.

Conventionally, a cutting tool in which a coating is coated on a base material has been used. For example, Japanese Patent Application Laid-Open No. 2004-284003 (Patent Document 1) discloses that when viewed in plan from the normal direction of the surface of a layer, the total area of crystal grains indicating the crystal orientation of the (0001) plane is 70% or more. It discloses a surface-coated cutting tool having a coating comprising -al ₂ O ₃ layer.

Japanese Patent Application Laid-Open No. 2009-028894 (Patent Document 2) discloses a coated cutting tool having a cemented carbide body and a coating, wherein at least the uppermost layer has a thickness of 7 to 12 μm (006). ) -Oriented α-Al ₂ O ₃ layer whose orientation coefficient TC (006) is greater than 2 and less than 6, and at the same time, the orientation coefficients TC (012), TC (110), TC ( 113), TC (202), TC (024) and TC (116) are all less than 1 and the orientation coefficient TC (104) is the second largest orientation coefficient disclosed.

JP 2004-284003 A JP 2009-028894 A

Cutting tool according to the present disclosure,
A cutting tool comprising a substrate having a rake face and a coating covering the rake face,
The coating includes an α-Al ₂ O ₃ layer provided on the substrate,
The α-Al ₂ O ₃ layer includes α-Al ₂ O ₃ crystal grains,
The α-Al ₂ O ₃ layer has an area ratio of the (001) -oriented crystal grains in the rake face of 50% or more and 90% or less,
In the measurement of residual stress by 2θ-sin ² ψ method using X-ray,
The residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −1000 MPa or more and less than 0 MPa,
The residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1000 MPa or more and less than 0 MPa,
| A _A | ≦ | B _A |

FIG. 1 is a perspective view illustrating one embodiment of a base material of a cutting tool. FIG. 2 is an example of a color map on the processed surface of the α-Al ₂ O ₃ layer. FIG. 3 is a schematic sectional view showing a region in the thickness direction of the α-Al ₂ O ₃ layer. FIG. 4 is a graph schematically showing a stress distribution in the thickness direction of the α-Al ₂ O ₃ layer. FIG. 5 is a schematic cross-sectional view showing an example of a chemical vapor deposition apparatus used for manufacturing a coating. FIG. 6 is a schematic sectional view of the cutting tool according to the present embodiment.

[Problems to be solved by the present disclosure]
In Patent Literature 1 and Patent Literature 2, wear resistance (for example, crater wear resistance) and fracture resistance of a surface-coated cutting tool are provided by having a coating including an α-Al ₂ O ₃ layer having the above-described configuration. It is expected that the mechanical properties such as the workability will be improved and the life of the cutting tool will be prolonged.

  However, in recent cutting processes, speeding and efficiency have been increased, the load on the cutting tool has increased, and the life of the cutting tool has tended to be shortened. Therefore, there is a demand for further improving the mechanical properties of the coating film of the cutting tool.

  The present disclosure has been made in view of the above circumstances, and it is an object of the present disclosure to provide a cutting tool having excellent fracture resistance and crater wear resistance.

[Effects of the present disclosure]
According to the present disclosure, it is possible to provide a cutting tool having excellent fracture resistance and crater wear resistance.

[Description of Embodiment of the Present Disclosure]
First, embodiments of the present disclosure will be listed and described.

[1] The cutting tool according to the present disclosure includes:
A cutting tool comprising a substrate having a rake face and a coating covering the rake face,
The coating includes an α-Al ₂ O ₃ layer provided on the substrate,
The α-Al ₂ O ₃ layer includes α-Al ₂ O ₃ crystal grains,
The α-Al ₂ O ₃ layer has an area ratio of the (001) -oriented crystal grains in the rake face of 50% or more and 90% or less,
In the measurement of residual stress by 2θ-sin ² ψ method using X-ray,
The residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −1000 MPa or more and less than 0 MPa,
The residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1000 MPa or more and less than 0 MPa,
| A _A | ≦ | B _A |

  By providing the above-described configuration, the cutting tool can have excellent fracture resistance and excellent crater wear resistance. Here, the “breakage resistance” means a property of suppressing destruction or falling off of a coating film from a substrate.

[2] The thickness of the α-Al ₂ O ₃ layer is 1 μm or more and 20 μm or less,
From the opposite side of the surface and the substrate in the α-Al ₂ O ₃ layer, a virtual plane located 10% of the distance d ₁₀ of the thickness of the α-Al ₂ O ₃ layer toward the base material side D1,
An imaginary plane located at a distance d ₄₀ of 40% of the thickness of the α-Al ₂ O ₃ layer from the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side D2,
In the residual stress measurement by the constant penetration depth method using X-rays in the region r1 sandwiched between
The residual stress A obtained based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −800 MPa or more and 600 MPa or less,
The residual stress B obtained based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1300 MPa or more and 400 MPa or less,
The relational expression of A> B is satisfied. By defining in this way, it becomes possible to provide a cutting tool having even more excellent fracture resistance.

[3] The stress distribution of the residual stress A is:
From the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side, a 1a region where the residual stress A continuously decreases,
A second a region in which the residual stress A continuously increases from the surface opposite to the substrate and from the surface opposite to the substrate toward the substrate. And
The first a region and the second a region are continuous via the minimum point of the residual stress A. By defining in this way, it is possible to provide a cutting tool having even more excellent crater wear resistance.

[4] The stress distribution of the residual stress B is:
A 1b region in which the residual stress B continuously decreases from the surface of the α-Al ₂ O ₃ layer opposite to the substrate toward the substrate;
A second b region in which the residual stress B continuously increases from the surface opposite to the substrate and toward the substrate from a surface opposite to the substrate. And
The 1b region and the 2b region are continuous via the minimum point of the residual stress B. By defining in this way, it is possible to provide a cutting tool having even more excellent crater wear resistance.

[5] The coating further includes one or more intermediate layers provided between the substrate and the α-Al ₂ O ₃ layer,
The intermediate layer includes at least one element selected from the group consisting of a group 4 element, a group 5 element, a group 6 element, Al and Si, and at least one element selected from the group consisting of C, N, B and O. Includes compounds consisting of species elements. By defining in this way, it becomes possible to provide a cutting tool having more excellent fracture resistance and crater wear resistance.

[Details of Embodiment of the Present Disclosure]
Hereinafter, an embodiment of the present disclosure (hereinafter, referred to as “the present embodiment”) will be described. However, the present embodiment is not limited to this. In the present specification, the notation of the form “X to Y” means the upper and lower limits of the range (that is, X or more and Y or less). When a unit is not described in X and a unit is described only in Y, X And the unit of Y are the same. Further, in the present specification, when a compound is represented by a chemical formula in which the composition ratio of the constituent elements is not limited, such as “TiC”, the chemical formula is represented by any conventionally known composition ratio (element ratio) Shall be included. At this time, the above chemical formula includes not only the stoichiometric composition but also the non-stoichiometric composition. For example, the chemical formula of “TiC” includes not only the stoichiometric composition “Ti ₁ C ₁ ” but also a non-stoichiometric composition such as “Ti ₁ C _0.8 ”. The same applies to the description of compounds other than “TiC”.

≪Cutting tool≫
Cutting tool according to the present disclosure,
A cutting tool comprising a substrate having a rake face and a coating covering the rake face,
The coating includes an α-Al ₂ O ₃ layer provided on the substrate,
The α-Al ₂ O ₃ layer includes α-Al ₂ O ₃ crystal grains,
The α-Al ₂ O ₃ layer has an area ratio of the (001) -oriented crystal grains in the rake face of 50% or more and 90% or less,
In the measurement of residual stress by 2θ-sin ² ψ method using X-ray,
The residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −1000 MPa or more and less than 0 MPa,
The residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1000 MPa or more and less than 0 MPa,
| A _A | ≦ | B _A |

  The surface-coated cutting tool of the present embodiment (hereinafter, may be simply referred to as “cutting tool”) includes a base material having a rake face, and a coating covering the rake face. In another aspect of the present embodiment, the coating may cover a portion (for example, a flank) of the base material other than the rake face. The cutting tools include, for example, drills, end mills, replaceable cutting tips for drills, replaceable cutting tips for end mills, replaceable cutting tips for milling, replaceable cutting tips for turning, metal saws, and gear cutting tools. , Reamer, tap, etc.

<Substrate>
As the substrate of the present embodiment, any conventionally known substrate of this type can be used. For example, the base material is made of a cemented carbide (for example, a tungsten carbide (WC) based cemented carbide, a cemented carbide containing Co in addition to WC, a carbonitride such as Cr, Ti, Ta, Nb in addition to WC) ), Cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic It is preferable to include at least one selected from the group consisting of a sintered boron nitride body (cBN sintered body) and a diamond sintered body. More preferably, the base material includes at least one selected from the group consisting of a cemented carbide, a cermet, and a cBN sintered body.

  Among these various substrates, it is particularly preferable to select a WC-based cemented carbide or a cBN sintered body. The reason for this is that these base materials have an excellent balance between hardness and strength, particularly at high temperatures, and have excellent properties as base materials for cutting tools for the above-mentioned applications.

  When a cemented carbide is used as a base material, the effect of the present embodiment is exhibited even if such a cemented carbide contains free carbon or an abnormal phase called an η phase in its structure. The substrate used in the present embodiment may have a modified surface. For example, in the case of a cemented carbide, a β-removed layer may be formed on the surface thereof, or in the case of a cBN sintered body, a surface hardened layer may be formed. The effects of the present embodiment are shown.

  FIG. 1 is a perspective view illustrating one embodiment of a base material of a cutting tool. The base material having such a shape is used, for example, as a base material of an exchangeable cutting edge for turning. The base material 10 has a rake face 1, a flank face 2, and a cutting edge ridge 3 at which the rake face 1 and the flank face 2 intersect. That is, the rake face 1 and the flank face 2 are faces that are connected to each other with the cutting edge ridgeline portion 3 interposed therebetween. The cutting edge ridge 3 constitutes the cutting edge of the base material 10. Such a shape of the base material 10 can be grasped as a shape of the cutting tool.

  When the cutting tool is a cutting edge-changeable cutting tip, the base material 10 may or may not have a chip breaker. The shape of the edge line 3 is a combination of a sharp edge (a ridge where the rake face and the flank intersect), honing (a sharp edge with a radius), a negative land (a chamfered), and honing and a negative land. Among them, all are included.

  As described above, the shape of the base material 10 and the name of each part have been described with reference to FIG. 1. However, in the cutting tool according to the present embodiment, the shape and the name of each part corresponding to the base material 10 are the same as above. Terms will be used. That is, the cutting tool 50 has a rake face 1, a flank 2, and a cutting edge 3 connecting the rake face 1 and the flank 2 (see FIG. 6).

<Coating>
The coating 40 according to the present embodiment includes the α-Al ₂ O ₃ layer 20 provided on the base material 10 (see FIG. 6). The “coating” covers at least a part of the rake face (for example, a part that comes into contact with a work material at the time of cutting), thereby improving the properties of the cutting tool such as chipping resistance and wear resistance. Have The coating preferably covers not only a part of the rake face but also the entire rake face. Further, the coating may cover the entire surface of the substrate. However, even if a part of the rake face is not covered with the coating or the configuration of the coating is partially different, it does not depart from the scope of the present embodiment.

The thickness of the coating is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 25 μm or less. Here, the thickness of the coating means the total thickness of the layers constituting the coating. Examples of the “layer constituting the film” include an α-Al ₂ O ₃ layer, an intermediate layer, an underlayer, and an outermost layer, which will be described later. For example, the thickness of the coating is measured by using a scanning transmission electron microscope (STEM) at any 10 points in a cross-sectional sample parallel to the normal direction of the surface of the substrate, and measuring the thickness of the 10 points. It can be obtained by taking the average of the values. The same applies to the case where the thickness of each of the α-Al ₂ O ₃ layer, the intermediate layer, the underlayer, the outermost layer, and the like described later is measured. Examples of the scanning transmission electron microscope include JEM-2100F (trade name) manufactured by JEOL Ltd.

(Α-Al ₂ O ₃ layer)
The α-Al ₂ O ₃ layer of the present embodiment includes crystal grains of α-Al ₂ O ₃ (aluminum oxide having an α-type crystal structure) (hereinafter sometimes simply referred to as “crystal grains”). That is, the α-Al ₂ O ₃ layer is a layer containing polycrystalline α-Al ₂ O ₃ .

The α-Al ₂ O ₃ layer may be provided directly above the base material or another layer such as an intermediate layer described below, as long as the effect of the cutting tool according to the present embodiment is not impaired. It may be provided on the base material through the intermediary. The α-Al ₂ O ₃ layer may have another layer such as an outermost layer provided thereon. Further, the α-Al ₂ O ₃ layer may be the outermost layer (outermost layer) of the coating.

The α-Al ₂ O ₃ layer has the following characteristics. That is, in the α-Al ₂ O ₃ layer, the area ratio of the (001) -oriented crystal grains in the rake face is 50% or more and 90% or less. In another aspect of the present embodiment, the area ratio of crystal grains other than the (001) -oriented crystal grains on the rake face is 10% or more and 50% or less. The sum of the area ratio of the (001) -oriented crystal grains and the area ratio of the crystal grains other than the (001) -oriented crystal grains is 100%.

In another alternative aspect of this embodiment, the α-Al ₂ O ₃ layer, the processing surface of the mirror-polished the α-Al ₂ O ₃ layer is parallel to the surface of the substrate in the rake face On the other hand, when the crystal orientation of each of the crystal grains is specified from the backscattered electron diffraction image analysis using a field emission scanning electron microscope, and a color map is created based on the crystal orientation, (001) The area ratio of the oriented crystal grains may be 50% or more and 90% or less.

Cutting tool according to the present embodiment, by crystal grains of the area ratio of the _α-Al 2 _{O 3} layer with (001) orientation was _α-Al 2 _{O 3} in the rake face is 90% or less than 50%, alpha -al ₂ O ₃ layer a certain orientation ((001) orientation) can sufficiently obtain the effect of improving the strength of the coating have. Further, when the coating covers the entire surface of the substrate, the cutting tool of the present embodiment includes (001) -oriented crystal grains in the α-Al ₂ O ₃ layer on a surface other than the rake surface of the substrate. May be 50% or more and 90% or less, or may be a value out of 50% or more and 90% or less.

Here, “(001) -oriented α-Al ₂ O ₃ crystal grains” or “(001) -oriented crystal grains” refers to the surface of the base material (the surface facing the coating film). Α-Al ₂ O ₃ crystal grains in which the inclination angle of the (001) plane (the angle between the normal of the substrate surface and the normal of the (001) plane) is 0 to 20 ° with respect to the normal. . Whether or not arbitrary α-Al ₂ O ₃ crystal grains are (001) -oriented in the α-Al ₂ O ₃ layer is determined by a field emission scanning type equipped with an electron beam backscatter diffraction device (EBSD device). It can be confirmed using an electron microscope (FE-SEM). Electron beam backscatter diffraction image analysis (EBSD image analysis) is an analysis method based on automatic analysis of a Kikuchi diffraction pattern generated by backscattered electrons. Incidentally, “crystal grains other than (001) -oriented α-Al ₂ O ₃ crystal grains” or “crystal grains other than (001) -oriented crystal grains” are (001) with respect to the normal line of the substrate surface. ) Means α-Al ₂ O ₃ crystal grains whose plane inclination angle exceeds 20 °.

For example, using a FE-SEM equipped with an EBSD device, an image of the mirror-polished α-Al ₂ O ₃ layer processed surface that is parallel to the surface of the base material on the rake face is taken. Next, the normal direction of the (001) plane of each pixel of the captured image and the normal direction of the substrate surface (that is, the linear direction parallel to the thickness direction of the α-Al ₂ O ₃ layer on the processed surface) Calculate the angle to make. Then, a pixel whose angle is 0 to 20 ° is selected. The selected pixel is composed of α-Al ₂ O ₃ crystal grains having a (001) plane inclination angle of 0 to 20 ° with respect to the substrate surface, that is, “(001) -oriented α-Al ₂ O _3. Of crystal grains.

Then, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in a predetermined region (that is, a color map) of the processed surface of the α-Al ₂ O ₃ layer is represented by α-Al as a crystal orientation mapping. to the working surface of the ₂ O ₃ layer, it is calculated based on the color map created by color-coding the selected pixels. In the crystal orientation mapping, a predetermined color is assigned to the selected pixel. Therefore, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in a predetermined region is determined by the assigned color. Can be calculated using as an index. The calculation of the angle formed, the selection of the pixel having the angle of 0 to 20 °, and the calculation of the area ratio are performed, for example, using commercially available software (trade name: “Orientation Imaging Microscopy Ver 6.2”, manufactured by EDAX). Can be performed.

FIG. 2 is an example of a color map relating to the processed surface of the α-Al ₂ O ₃ layer 20. In FIG. 2, a region surrounded by a solid line and indicated by hatching with left diagonal lines is a (001) -oriented crystal grain 21, and each region surrounded by a solid line and indicated by white is other than the (001) -oriented crystal grain. Are the crystal grains 22. That is, in the color map illustrated in FIG. 2, the crystal grains having an angle of 0 to 20 ° in the normal direction of the (001) plane with respect to the normal direction of the surface of the α-Al ₂ O ₃ layer 20 are hatched with left diagonal lines. Indicated by Further, the crystal grains whose normal direction of the (001) plane with respect to the normal of the surface of the α-Al ₂ O ₃ layer 20 exceeds 20 ° are shown in white.

From the above crystal orientation mapping (color map), in the present embodiment, the α-Al ₂ O ₃ layer has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 50% or more and 90% in the processed surface. % Or less. The area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is preferably 50% or more and 90% or less, and more preferably 55% or more and 85% or less.

When calculating the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains, the observation magnification of the FE-SEM is 5000 times. The observation area is 450 μm ² (30 μm × 15 μm). The number of measurement visual fields is 3 or more.

The thickness of the α-Al ₂ O ₃ layer is preferably 1 μm or more and 20 μm or less, more preferably 4 μm or more and 15 μm or less.

(Residual stress of α-Al ₂ O ₃ layer)
(Residual stress in film by 2θ-sin ² ψ method)
The α-Al ₂ O ₃ layer according to the present embodiment has a residual stress measured by a 2θ-sin ² ψ method using X-rays.
The residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −1000 MPa or more and less than 0 MPa,
The residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1000 MPa or more and less than 0 MPa,
| A _A | ≦ | B _A | (Equation 1) is satisfied.

  Here, “residual stress” is a type of internal stress (intrinsic strain) existing in the layer. The residual stress is roughly classified into a compressive residual stress and a tensile residual stress. The compressive residual stress refers to a residual stress represented by a numerical value of “−” (minus) (in the present specification, the unit is represented by “MPa”). For example, “a compressive residual stress of 100 MPa” can be understood as a residual stress of −100 MPa. For this reason, the concept that the compressive residual stress is large indicates that the absolute value of the numerical value is large, and the concept that the compressive residual stress is small indicates that the absolute value of the numerical value is small. Incidentally, the tensile residual stress refers to a residual stress represented by a numerical value of “+” (plus) (the unit is represented by “MPa” in this specification). For example, “100 MPa tensile residual stress” can be grasped as 100 MPa residual stress. For this reason, the concept that the tensile residual stress is large indicates that the numerical value increases, and the concept that the tensile residual stress is small indicates that the numerical value decreases.

In the present embodiment, the “residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane on the rake face” is a residual stress reflecting the entire predetermined measurement visual field on the rake face, It means the residual stress obtained based on the crystal plane interval of the (001) plane in the entire predetermined measurement visual field. The film residual stress A _A is determined by the residual stress measurement by 2θ-sin ² ψ method using an X-ray. As a specific method, first, the crystal plane interval of the (001) plane is measured by the 2θ-sin ² ψ method over the entire measurement visual field. Here, the diffraction angle at the time of measurement specifies a diffraction angle corresponding to the crystal plane of the measurement object. The above-mentioned measurement visual field means “the measurement visual field on the surface of the α-Al ₂ O ₃ layer”. Next, the residual stress in the entire measurement visual field is calculated based on the measured crystal plane spacing of the (001) plane. Such measurement is performed in a plurality of measurement visual fields, and the average value of the residual stress obtained in each measurement visual field is defined as “residual stress in film A _A ”.
(001) when oriented crystal grains of the area ratio is 50% or more, the film residual stress A _A is considered to be large contribution of residual stress of the crystal grains oriented (001). Under such circumstances, the film residual stress A _A believes the present inventors to be able also to grasp the residual stress of the crystal grains oriented (001).

In the present embodiment, the residual stress measurement by the 2θ-sin ² ψ method is performed under the following conditions.
Apparatus: SmartLab (Rigaku Corporation)
X-ray: Cu / Kα / 45 kV / 200 mA
Counter: D / teX Ultra250 (manufactured by Rigaku Corporation)
Scanning range: For membrane residual stress _{A A} 89.9 ° _~91.4 ° (gradient method)
In the case of residual stress B _{A in} the film 37.0 ° to 38.4 ° (tilt method)

In the present embodiment, the “residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane in the rake face” is a residual stress that reflects the entire predetermined measurement visual field in the rake face, and It means the residual stress determined based on the crystal plane spacing of the (110) plane in the entire predetermined measurement visual field. The residual stress B _{A in the} film is determined by measuring the residual stress by the 2θ-sin ² ψ method using X-rays. As a specific method, first, the crystal plane spacing of the (110) plane is measured by the 2θ-sin ² ψ method over the entire measurement visual field. Here, the above-mentioned measurement visual field means “the measurement visual field on the surface of the α-Al ₂ O ₃ layer”. Next, the residual stress in the entire measurement visual field is calculated based on the measured crystal plane spacing of the (110) plane. Such measurement is performed in a plurality of measurement visual fields, and the average value of the residual stress obtained in each measurement visual field is defined as “residual stress B _{A in the} film”.
The residual stress B _A in the film tends to show a higher compressive residual stress value than the residual stress A _{A in the} film. Under such circumstances, the inventors of the present invention have concluded that the residual stress B _A in the film has a larger contribution of the residual stress of crystal grains other than the (001) -oriented crystal grains as compared with the residual stress A _{A in the} film. thinking.

(Residual stress of α-Al ₂ O ₃ layer in depth direction)
(Residual stress by the constant penetration depth method)
In this embodiment, a distance d ₁₀ of 10% of the thickness of the α-Al ₂ O ₃ layer from the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side. A virtual plane D1 located at
An imaginary plane located at a distance d ₄₀ of 40% of the thickness of the α-Al ₂ O ₃ layer from the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side D2,
In the residual stress measurement by the constant penetration depth method using X-rays in the region r1 sandwiched between
The residual stress A obtained based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −800 MPa or more and 600 MPa or less,
The residual stress B obtained based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1300 MPa or more and 400 MPa or less,
It is preferable to satisfy the relational expression of A> B (Expression 2) (for example, FIG. 3).
In another aspect of the present embodiment, the thickness of the α-Al ₂ O ₃ layer is 1 μm or more and 20 μm or less;
From the opposite side of the surface and the substrate in the α-Al ₂ O ₃ layer, a virtual plane located 10% of the distance d ₁₀ of the thickness of the α-Al ₂ O ₃ layer toward the base material side D1,
An imaginary plane located at a distance d ₄₀ of 40% of the thickness of the α-Al ₂ O ₃ layer from the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side D2,
In the residual stress measurement by the constant penetration depth method using X-rays in the region r1 sandwiched between
The residual stress A obtained based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −800 MPa or more and 600 MPa or less,
The residual stress B obtained based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1300 MPa or more and 400 MPa or less,
It is preferable to satisfy the relational expression of A> B.

In the present embodiment, the “residual stress A obtained based on the crystal plane spacing of the (001) plane on the rake plane” is the residual stress at a predetermined depth position on the rake plane, and the crystal of the (001) plane It means the residual stress obtained based on the plane distance. The residual stress A is obtained by a constant penetration depth method using X-rays. As a specific method, first, the crystal plane interval of the (001) plane at a predetermined depth position is measured by the constant penetration depth method for the entire measurement visual field. Here, the above-mentioned measurement visual field means “a measurement visual field in a virtual plane parallel to the surface of the α-Al ₂ O ₃ layer and passing through a predetermined depth position”. Next, the residual stress in the entire measurement visual field is calculated based on the measured crystal plane spacing of the (001) plane. Such a measurement is performed in a plurality of measurement visual fields, and the average value of the residual stress obtained in each measurement visual field is defined as “residual stress A”.

In the present embodiment, the residual stress measurement by the constant penetration depth method is performed under the following conditions.
Apparatus: Spring-8 BL16XU
X-ray energy: 10 keV (λ = 0.124 nm)
X-ray beam diameter: 0.4 to 1.8 mm (changes depending on penetration depth)
Diffraction surface used: In the case of residual stress A_ (001) plane
In the case of residual stress B_ (110) plane

  In the present embodiment, the “residual stress B obtained based on the crystal plane spacing of the (110) plane on the rake face” is the residual stress at a predetermined depth position on the rake face, and It means the residual stress obtained based on the plane distance. The residual stress B is obtained by a constant penetration depth method using X-rays.

In the region r1, it is determined whether the residual stress A and the residual stress B are each a residual stress within a predetermined numerical range and satisfy the relational expression of the above expression 2, for example, by the penetration depth using X-rays. the residual stress a _{(respectively, a d10,} a _d40) at the depth position and depth position of a predetermined distance _{d 40} a predetermined distance _{d 10} of the _α-Al 2 _{O 3} layer by a constant method and the residual stress B (B _d10 , B _d40 , respectively) can be determined. That is, (1) First, the residual stress A _d10 and the residual stress B _d10 in a certain measurement visual field on the virtual plane D1 are measured by a constant penetration depth method. (2) Next, the residual stress A _d40 and the residual stress B _d40 in the visual field on the virtual plane D2 located in the same region as a certain measurement visual field on the virtual plane D1 and located immediately below the measurement visual field are similarly calculated. Measure by the constant penetration depth method. (3) When the measured residual stresses _Ad10 and _Ad40 , and the residual stresses _Bd10 and _Bd40 are respectively in the numerical ranges described above, and _Ad10 > _Bd10 and _Ad40 > _Bd40 , In the region r1, the residual stress A and the residual stress B are in the above-described numerical range and satisfy the relational expression of the above-described Expression 2. "

(Residual stress distribution of α-Al ₂ O ₃ layer)
In the α-Al ₂ O ₃ layer 20 according to the present embodiment, the stress distribution of the residual stress A is from the surface of the α-Al ₂ O ₃ layer opposite to the substrate toward the substrate. A 1a region in which the residual stress A continuously decreases;
A second a region in which the residual stress A continuously increases from the surface opposite to the substrate and from the surface opposite to the substrate toward the substrate. And
It is preferable that the first a region and the second a region are continuous via the minimum point of the residual stress A.

FIG. 4 shows an example of the stress distribution. In the graph of FIG. 4, the vertical axis indicates the residual stress, and the horizontal axis indicates the position of the α-Al ₂ O ₃ layer 20 in the thickness direction. With respect to the vertical axis, when the value is “−”, it means that a compressive residual stress exists in the α-Al ₂ O ₃ layer 20, and when the value is “+”, the α-Al ₂ O ₃ layer 20 means that there is a tensile residual stress. If the value is “0”, it means that no stress exists in the α-Al ₂ O ₃ layer 20.

Referring to FIG. 4, the stress distribution (curve a in FIG. 4) of the residual stress A in the thickness direction in the α-Al ₂ O ₃ layer 20 is, for example, the upper surface side (surface side or the surface opposite to the base material). Side) to the lower surface side (substrate side), a first a region P1a in which the value of the residual stress continuously decreases, and a lower surface side than the first a region, and from the upper surface side to the lower surface side. And a second a region P2a in which the value of the residual stress continuously increases. Here, there is a point in the 2a region where the residual stress changes from a compressive residual stress to a tensile residual stress. It is preferable that the first a region and the second a region are continuous via a minimum point P3a at which the value of the residual stress becomes minimum. The minimum point P3a is located closer to the upper surface than to the lower surface.

Since the α-Al ₂ O ₃ layer 20 has the above-described stress distribution, the balance between the crater wear resistance and the fracture resistance of the α-Al ₂ O ₃ layer 20 during interrupted cutting is more excellent. Become. This impact applied from the upper surface of the _α-Al 2 _{O 3} layer 20 in _α-Al 2 _{O 3} layer 20, while being well absorbed in between the upper surface side of the minimum point P3a, than minimum point P3a This is because high adhesion is exhibited on the lower surface side.

  In the stress distribution of the residual stress A, the value of the residual stress is preferably in a range from −1000 MPa to 2000 MPa. In other words, in the stress distribution of the residual stress A, the absolute value of the compressive residual stress is 1000 MPa or less (that is, −1000 MPa or more and less than 0 MPa), and the absolute value of the tensile residual stress is 2000 MPa or less (that is, more than 0 MPa and 2000 MPa or less). It is preferred that In this case, both properties of crater wear resistance and fracture resistance tend to be appropriately exhibited.

The minimum point P3a is preferably located at a distance of 0.1 to 40% of the thickness of the α-Al ₂ O ₃ layer 20 from the surface (upper surface) on the side opposite to the substrate. In this case, the damage form of the α-Al ₂ O ₃ layer 20 is stabilized, and for example, sudden loss can be suppressed, and thus, variation in tool life can be reduced. For example, when the thickness of the α-Al ₂ O ₃ layer 20 is 1 to 20 μm, the position of the minimum point P3a is preferably 0.1 to 8 μm from the surface on the opposite side to the substrate. The absolute value of the compressive residual stress at the minimum point P3a is preferably from 100 to 900 MPa, more preferably from 200 to 890 MPa, and further preferably from 350 to 890 MPa. In other words, the value of the residual stress at the minimum point P3a is preferably −900 to −100 MPa, more preferably −890 to −200 MPa, and still more preferably −890 to −350 MPa.

In the present embodiment, the stress distribution of the residual stress B is such that the residual stress B continuously decreases from the surface of the α-Al ₂ O ₃ layer opposite to the substrate toward the substrate. A first b region,
A second b region in which the residual stress B continuously increases from the surface opposite to the substrate and toward the substrate from a surface opposite to the substrate. And
It is preferable that the first region b and the second region b are continuous via the minimum point of the residual stress B.

  In the stress distribution of the residual stress B, the value of the residual stress is preferably in the range of −1300 MPa to 2000 MPa. In other words, in the stress distribution of the residual stress B, the absolute value of the compressive residual stress is 1300 MPa or less (that is, -1300 MPa or more and less than 0 MPa), and the absolute value of the tensile residual stress is 2000 MPa or less (that is, more than 0 MPa and 2000 MPa or less). It is preferred that In this case, both properties of crater wear resistance and fracture resistance tend to be appropriately exhibited.

The minimum point P3b is preferably located at a distance of 0.1 to 40% of the thickness of the α-Al ₂ O ₃ layer 20 from the surface (upper surface) on the side opposite to the base. In this case, the damage form of the α-Al ₂ O ₃ layer 20 is stabilized, and for example, sudden loss can be suppressed, and thus, variation in tool life can be reduced. For example, when the thickness of the α-Al ₂ O ₃ layer 20 is 1 to 20 μm, the position of the minimum point P3b is preferably 0.1 to 8 μm from the surface on the side opposite to the base. Further, the absolute value of the compressive residual stress at the minimum point P3b is preferably from 150 to 1250 MPa, more preferably from 250 to 1100 MPa, and still more preferably from 400 to 1000 MPa. In other words, the value of the residual stress at the minimum point P3b is preferably -1250 to -150 MPa, more preferably -1100 to -250 MPa, and still more preferably -1000 to -400 MPa.

(Average particle size of α-Al ₂ O ₃ crystal grains)
In the present embodiment, the α-Al ₂ O ₃ crystal grains preferably have an average particle diameter of 0.1 μm to 3 μm, and more preferably 0.2 μm to 2 μm. The average grain size of the crystal grains can be determined, for example, using the color map. Specifically, first, in the above-described color map, a region in which colors match (that is, the plane orientations match) and the periphery of which is surrounded by another color (that is, another plane orientation) is defined as a region of each crystal grain. Regarded as a separate area. Next, the distance between two points on the outer periphery of each crystal grain is measured, and the distance between the two longest points is defined as the particle size of each crystal grain.

(Intermediate layer)
The coating preferably further includes one or more intermediate layers provided between the substrate and the α-Al ₂ O ₃ layer. The intermediate layer includes at least one element selected from the group consisting of a group 4 element, a group 5 element, a group 6 element, Al and Si, and at least one element selected from the group consisting of C, N, B and O. It is preferable to include a compound composed of the element of the species. Examples of Group 4 elements of the periodic table include titanium (Ti), zirconium (Zr), hafnium (Hf), and the like. Examples of group 5 elements of the periodic table include vanadium (V), niobium (Nb), tantalum (Ta), and the like. Examples of Group 6 elements in the periodic table include chromium (Cr), molybdenum (Mo), and tungsten (W). More preferably, the intermediate layer contains a Ti compound comprising a Ti element and at least one element selected from the group consisting of C, N, B and O.

Examples of the compound contained in the intermediate layer include TiCNO, TiAlN, TiAlSiN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrSiN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlTiVN, TiB ₂ , TiCrHfN, AlSiN , AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiAlBN, TiAlCrSiBCNO, ZrN and ZrCN.

  The thickness of the intermediate layer is preferably from 0.1 μm to 3 μm, more preferably from 0.5 μm to 1.5 μm.

(Other layers)
The coating may further include another layer as long as the effect of the cutting tool according to the present embodiment is not impaired. The composition of the other layer may be different or the same as that of the α-Al ₂ O ₃ layer or the intermediate layer. Examples of the compound contained in the other layer include TiN, TiCN, TiBN, Al ₂ O _{3, and the} like. The order of the other layers is not particularly limited. For example, as the other layer, undercoat layer provided between the substrate and the α-Al ₂ O ₃ layer, the outermost layer or the like provided on the α-Al ₂ O ₃ layer Is mentioned. The thickness of the other layers is not particularly limited as long as the effects of the present embodiment are not impaired, and is, for example, 0.1 μm or more and 20 μm or less.

製造 Method of manufacturing cutting tools 工具
The manufacturing method of the cutting tool according to the present embodiment,
A step of preparing the base material having a rake face (hereinafter, may be referred to as a “first step”);
Forming a film including the α-Al ₂ O ₃ layer on the rake face of the base material using a chemical vapor deposition method (hereinafter, may be referred to as “second step”);
A step of blasting the α-Al ₂ O ₃ layer on the rake face (hereinafter, may be referred to as a “third step”);
including.

<First step: Step of preparing base material>
In the first step, a base material having a rake face is prepared. For example, a cemented carbide substrate is prepared as a substrate. The cemented carbide substrate may be a commercially available one, or may be manufactured by a general powder metallurgy method. When manufacturing by a general powder metallurgy method, for example, a WC powder and a Co powder are mixed by a ball mill or the like to obtain a mixed powder. After the mixed powder is dried, it is molded into a predetermined shape to obtain a molded body. Further, by sintering the compact, a WC-Co-based cemented carbide (sintered body) is obtained. Next, a base material made of a WC-Co-based cemented carbide can be manufactured by subjecting the sintered body to a predetermined cutting edge such as honing. In the first step, any substrate other than those described above can be prepared as long as it is a conventionally known substrate of this type.

<Second step: Step of forming a coating>
In the second step, a film including the α-Al ₂ O ₃ layer is formed on the rake face of the substrate by using a chemical vapor deposition method (CVD method).

FIG. 5 is a schematic cross-sectional view showing an example of a chemical vapor deposition apparatus (CVD apparatus) used for manufacturing a coating. Hereinafter, the second step will be described with reference to FIG. The CVD apparatus 30 includes a plurality of base material setting jigs 31 for holding the base material 10 and a reaction vessel 32 made of heat-resistant alloy steel that covers the base material setting jigs 31. A temperature controller 33 for controlling the temperature inside the reaction vessel 32 is provided around the reaction vessel 32. The reaction vessel 32 is provided with a gas introduction pipe 35 having a gas introduction port 34. The gas introduction pipe 35 extends in the vertical direction in the internal space of the reaction vessel 32 in which the base material setting jig 31 is arranged, and is disposed so as to be rotatable around the vertical direction. A plurality of jet holes 36 for jetting into the inside are provided. Using this CVD apparatus 30, each layer including the α-Al ₂ O ₃ layer constituting the coating film can be formed as follows.

First, the base material 10 is placed on the base material setting jig 31, and while controlling the temperature and pressure in the reaction vessel 32 within a predetermined range, the raw material gas for the α-Al ₂ O ₃ layer 20 is supplied to the gas introduction pipe 35. From the reaction vessel 32. Thereby, the α-Al ₂ O ₃ layer 20 is formed on the rake face of the base material 10. Here, before forming the α-Al ₂ O ₃ layer 20, the intermediate layer is formed on the surface of the base material 10 by introducing a raw material gas for the intermediate layer into the reaction vessel 32 from the gas introduction pipe 35. Is preferred. Hereinafter, a method for forming the α-Al ₂ O ₃ layer 20 after forming the intermediate layer on the surface of the substrate 10 will be described.

The raw material gas for the intermediate layer is not particularly limited. For example, a mixed gas of TiCl ₄ and N _2, a mixed gas of TiCl ₄ , N ₂ and CH ₃ CN, and a mixed gas of TiCl ₄ , N ₂ , CO and CH ₄ mixed gas.

The temperature in the reaction vessel 32 when forming the intermediate layer is preferably controlled to 1000 to 1100 ° C., and the pressure in the reaction vessel 32 is preferably controlled to 0.1 to 1013 hPa. Further, HCl gas may be introduced together with the above-mentioned source gas. By introducing HCl gas, the uniformity of the thickness of each layer can be improved. Note that H ₂ is preferably used as a carrier gas. Further, at the time of gas introduction, it is preferable to rotate the gas introduction pipe 35 by a driving unit (not shown). Thereby, each gas can be uniformly dispersed in the reaction vessel 32.

  Further, the intermediate layer may be formed by an MT (Medium Temperature) -CVD method. The MT-CVD method differs from the CVD method (hereinafter, also referred to as “HT-CVD method”) performed at a temperature of 1000 to 1100 ° C., in which the temperature in the reaction vessel 32 is relatively low, such as 850 to 950 ° C. This is a method of forming a layer while maintaining the temperature. Since the MT-CVD method is performed at a relatively low temperature as compared with the HT-CVD method, damage to the substrate 10 due to heating can be reduced. In particular, when the intermediate layer is a TiCN layer, the intermediate layer is preferably formed by the MT-CVD method.

Next, the α-Al ₂ O ₃ layer 20 is formed on the intermediate layer. As a source gas, a mixed gas of AlCl ₃ , N ₂ , CO ₂ and H ₂ S is used. At this time, the flow rate (L / min) between CO ₂ and H ₂ S is set to a flow rate ratio that satisfies CO ₂ / H ₂ S ≧ 2. Thereby, an α-Al ₂ O ₃ layer is formed. The upper limit of CO ₂ / H ₂ S is not particularly limited, but is preferably 5 or less from the viewpoint of uniformity of the thickness of the layer. Further, the present inventors have found that the preferable flow rates of CO ₂ and H ₂ S are 0.4 to 2.0 L / min and 0.1 to 0.8 L / min, most preferably 1 L / min and 0 L / min. It was confirmed to be 0.5 L / min.

The temperature in the reaction vessel 32 is preferably controlled to 1000 to 1100 ° C., and the pressure in the reaction vessel 32 is preferably controlled to 0.1 to 100 hPa. Further, HCl gas may be introduced together with the above-listed source gases, and H ₂ may be used as a carrier gas. It is to be noted that the rotation of the gas introduction pipe 35 during the gas introduction is preferably the same as described above.

From the viewpoint of further improving the effect of the present disclosure, a time of 90 minutes or more and 180 minutes or less at the end of the step of forming the α-Al ₂ O ₃ layer (hereinafter, may be referred to as “temperature decreasing time”), preferably 120 minutes. It is preferable that the temperature in the reaction vessel is continuously lowered at a rate of 0.3 to 0.5 ° C./min (hereinafter, sometimes referred to as “cooling rate”) for a time of 180 minutes or less. As a result, the tensile residual stress generated in the coating film is reduced, and it becomes possible to more effectively introduce a compressive stress in a subsequent blasting process.

Note that an outermost layer may be formed on the α-Al ₂ O ₃ layer 20 as long as the effect of the cutting tool according to the present embodiment is not impaired. The method of forming the outermost layer is not particularly limited, and examples thereof include a method of forming the outermost layer by a CVD method or the like.

In the above manufacturing method, the mode of each layer changes by controlling each condition of the CVD method. For example, the composition of each layer is determined by the composition of the raw material gas introduced into the reaction vessel 32, and the thickness of each layer is controlled by the execution time (film formation time). Above all, in order to reduce the proportion of coarse particles in the α-Al ₂ O ₃ layer 20 or to increase the (001) plane orientation, the flow rate ratio between CO ₂ gas and H ₂ S gas in the source gas is required. Control of (CO ₂ / H ₂ S) is important.

<Third step: Blasting step>
In the blasting step, the α-Al ₂ O ₃ layer on the rake face is blasted. "Blasting treatment" is a process in which a large number of small spheres (media) such as steel or non-ferrous metal (for example, ceramics) are made to collide (project) with a surface such as a rake face at a high speed, thereby causing the orientation and compression of the surface. It means a process that changes various properties such as stress. In the present embodiment, by performing blasting on the rake face, a residual stress is applied to the α-Al ₂ O ₃ layer on the rake face, and the difference between the residual stress A _A in the film and the residual stress B _{A in the} film is reduced. to be born. As a result, the crack growth of the α-Al ₂ O ₃ layer is suppressed, and the fracture resistance is excellent. There is no particular limitation on the projection of the medium as long as the residual stress A _{A in the} film and the residual stress B _A in the film in the α-Al ₂ O ₃ layer satisfy the relational expression of the above formula 1, and there is no particular limitation. _It may be performed directly on the ₂ O ₃ layer, or may be performed on another layer (for example, the outermost layer) provided on the α-Al ₂ O ₃ layer. There is no particular limitation as long as the projection of the medium is performed at least on the rake face. For example, the projection of the medium may be performed over the entire surface of the cutting tool.

Conventionally, blasting has been performed mainly to convert tensile stress remaining in a target layer in the coating into compressive stress. However, the residual stress in the film of the (001) oriented crystal grains (residual stress in the film A _A ) and the residual stress in the film of crystal grains other than the (001) oriented crystal grains (residual stress in the film B _A ) It has not been known until now that the blast process is performed to satisfy the above relational expression 1, and the present inventors have found for the first time.
Further, in the conventional blasting, the coating pressure is high and the coating is polished at the same time. Therefore, when the conventional blast treatment is performed, there is a tendency that the target layer is destroyed with the polishing of the coating film. In the present embodiment, the tensile residual stress generated in the α-Al ₂ O ₃ layer in the second step is smaller than the tensile residual stress of the α-Al ₂ O ₃ layer formed by the conventional manufacturing method. Therefore, _alpha-Al 2 without occur _{O 3} layer destruction of the stress is easily introduced into the _alpha-Al 2 _{O 3} layer, resulting membrane residual stress _{A A} and film residual stress _{B A} and the above formula 1 Can be satisfied.

The mechanism by which the residual stress A _A in the film and the residual stress B _{A in the} film satisfy the relational expression of the above expression 1 by performing the blast treatment on the α-Al ₂ O ₃ layer is not clear. Thinks as follows. The (001) -oriented crystal grains are mutually supported by crystal grains oriented in the same crystal orientation, and thus are considered to have resistance to deformation from external force. On the other hand, since the crystal grains other than the (001) -oriented crystal grains do not have the same crystal orientation, it is considered that resistance to deformation from external force is reduced. As described above, since the (001) -oriented crystal grains are different from the other crystal grains in the susceptibility to deformation from external force, a difference is generated in the residual stress applied by the blast treatment, and as a result, the film It is considered that the medium residual stress A _A and the film residual stress B _A satisfy the relational expression of the above equation 1.

  Examples of the material of the medium include steel, ceramics, aluminum oxide, and zirconium oxide.

  The average particle size of the media is, for example, preferably from 1 to 300 μm, and more preferably from 5 to 200 μm.

  Commercial media may be used as the medium, and examples thereof include ceramic abrasive grains having a particle diameter of 90 to 125 μm (average particle diameter of 100 μm) (manufactured by NITSU CORPORATION, trade name: WAF120).

  The distance between the projection unit for projecting the medium and the surface such as the rake face (hereinafter sometimes referred to as “projection distance”) is preferably from 80 mm to 120 mm, and more preferably from 80 mm to 100 mm. .

  The pressure applied to the medium during projection (hereinafter, sometimes referred to as “projection pressure”) is preferably 0.05 MPa to 0.5 MPa, more preferably 0.05 MPa to 0.3 MPa. .

  The blast processing time is preferably 5 seconds to 60 seconds, and more preferably 10 seconds to 30 seconds.

  Each condition of the blast processing described above can be appropriately adjusted according to the configuration of the coating.

<Other steps>
In the manufacturing method according to the present embodiment, in addition to the above-described steps, additional steps may be appropriately performed as long as the effects of the blast treatment are not impaired.

  Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

≫Making cutting tools≫
<First step: Step of preparing base material>
As a base material, a cemented carbide of a composition (but including unavoidable impurities) composed of TaC (2.0% by mass), NbC (1.0% by mass), Co (10.0% by mass) and WC (remainder). A cutting tip (shape: CNMG120408N-UX, manufactured by Sumitomo Electric Hardmetal Corporation, JIS B4120 (2013)) was prepared.

<Second step: Step of forming a coating>
On the prepared base material, an intermediate layer and an α-Al ₂ O ₃ layer were formed in this order using a CVD apparatus, and a coating was formed on the surface of the base material including the rake face. In some of the samples, the α-Al ₂ O ₃ layer was formed directly on the base material without forming the intermediate layer (sample numbers 8 and 13). The conditions for forming each layer are shown below. In the formation of the α-Al ₂ O ₃ layer, the temperature was lowered at the temperature decreasing rate shown in Table 2 during the temperature decreasing time shown in Table 2 at the end stage. In Table 2, "-" indicates that the corresponding process was not performed. The value in parentheses following each gas composition indicates the flow rate (L / min) of each gas. Table 1 shows the thickness of the α-Al ₂ O ₃ layer, and the thickness and composition of the intermediate layer.

(Intermediate layer)
Source gas: TiCl ₄ (0.002 L / min), CH ₄ (2.0 L / min), CO (0.3 L / min), N ₂ (6.5 L / min), HCl (1.8 L / min) , H ₂ (50 L / min)
Pressure: 160hPa
Temperature: 1000 ° C
Film formation time: 45 minutes

(Α-Al ₂ O ₃ layer)
Source gas: AlCl ₃ (2.4 L / min), CO ₂ (1.0 L / min), H ₂ S (1.5 L / min), H ₂ (35 L / min)
Pressure: 70hPa
Temperature: 950-1000 ° C
Temperature drop rate: As shown in Table 2, Temperature drop time: As shown in Table 2, Film formation time: 360 minutes

<Third step: Blasting step>
Next, the cutting tip (cutting tool) on which the coating was formed was subjected to blasting on the surface of the cutting tip including the rake face under the following conditions. In Table 2, "-" indicates that the corresponding process was not performed.
(Blast condition)
Abrasive grain concentration: 5-20 wt%
Projection pressure: as described in Table 2 Projection time: 5 to 15 seconds

  By the above procedure, cutting tools of sample numbers 1 to 8 (Example) and sample numbers 11 to 13 (Comparative Example) were produced.

特性 Evaluation of cutting tool characteristics≫
Using the cutting tools of Sample Nos. 1 to 8 and Sample Nos. 11 to 13 manufactured as described above, the characteristics of the cutting tools were evaluated as follows.

<Creating a color map>
Mirror polishing was performed on the rake face of the cutting tool provided with the coating so as to be parallel to the surface of the base material to produce a processed surface of an α-Al ₂ O ₃ layer. The above-mentioned color map was created for a processed surface of 30 μm × 15 μm by observing the manufactured processed surface at a magnification of 5000 times using an FE-SEM equipped with EBSD. The number of color maps (the number of measurement visual fields) created at this time was 3. Then, for each color map, using (001) oriented α-Al ₂ O ₃ crystal grains and (001) using commercially available software (trade name: “Orientation Imaging Microscopy Ver 6.2”, manufactured by EDAX) ) The area ratio occupied by each crystal grain other than the oriented α-Al ₂ O ₃ crystal grains was determined. Table 1 shows the results. As is clear from Table 1, in each color map, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains to the area of the entire color map, and the (001) -oriented α-Al ₂ The total area ratio of the crystal grains other than the O ₃ crystal grains was 100%.

<Measurement of residual stress in film by 2θ-sin ² ψ method>
The residual stress A _{A in the} film and the residual stress B _A in the film in the α-Al ₂ O ₃ layer were measured by the above-mentioned 2θ-sin ² ψ method under the following conditions. Table 4 shows the measured residual stress A _{A in the} film and residual stress B _{A in the} film. In Table 4, a residual stress represented by a negative value means a compressive residual stress, and a residual stress represented by a positive value means a tensile residual stress.
Apparatus: SmartLab (Rigaku Corporation)
X-ray: Cu / Kα / 45 kV / 200 mA
Counter: D / teX Ultra250 (manufactured by Rigaku Corporation)
Scanning range: For membrane residual stress _{A A} 89.9 ° _~91.4 ° (gradient method)
In the case of residual stress B _{A in} the film 37.0 ° to 38.4 ° (tilt method)

<Measurement of residual stress by constant penetration depth method>
Further, the residual stress A and the residual stress B at a predetermined depth position in the α-Al ₂ O ₃ layer were measured by the constant penetration depth method under the following conditions. Table 3 shows residual stresses A ( _Ad10 , _Ad40 ) and residual stresses B ( _Bd10 , _Bd40 ) at typical depth positions. It was confirmed whether or not each sample had the first-a region P1a and the second-a region P2a (the first-b region P1b and the second-b region P2b). In addition, it was determined that the minimum point P3b was present for the sample in which the first b region P1b and the second b region P2b were confirmed (Table 3).
Apparatus: Spring-8 BL16XU
X-ray energy: 10 keV (λ = 0.124 nm)
X-ray beam diameter: 0.4 to 1.8 mm (changes depending on penetration depth)
Diffraction surface used: In the case of residual stress A_ (001) plane
In the case of residual stress B_ (110) plane

≪Cutting test≫
(Intermittent processing test)
Using the cutting tools of Sample Nos. 1 to 8 and Sample Nos. 11 to 13 prepared as described above, the cutting time until the chip was chipped was measured under the following cutting conditions. Table 4 shows the results. A longer cutting time can be evaluated as a cutting tool having more excellent fracture resistance.
Test conditions for interrupted machining Work material: SCM415 groove material Cutting speed: 150 m / min
Feed: 0.2mm / rev
Cut: 2mm
Cutting oil: Wet

(Continuous processing test)
Using the cutting tools of Sample Nos. 1 to 8 and Sample Nos. 11 to 13 produced as described above, the cutting time until the crater wear depth reached 0.1 mm was measured under the following cutting conditions. Table 4 shows the results. A longer cutting time can be evaluated as a cutting tool having excellent crater wear resistance.
Test conditions for continuous machining Work material: SCM435 round bar Cutting speed: 250 m / min
Feed: 0.25mm / rev
Cut: 2mm
Cutting oil: Wet

  From the results shown in Table 4, the cutting tools of Examples Nos. 1 to 8 (Examples) showed good results with a cutting time of 5 minutes or more in intermittent machining. On the other hand, the cutting tools of Sample Nos. 11 to 13 (Comparative Examples) had a cutting time of less than 5 minutes in intermittent machining. From the above results, it was found that the cutting tools of the examples (sample numbers 1 to 8) had excellent fracture resistance.

  From the results in Table 4, the cutting tools of Examples Nos. 1 to 8 (Examples) obtained good results in which the cutting time in continuous machining was 20 minutes or more. On the other hand, the cutting time of the cutting tools of Sample Nos. 11 to 13 (Comparative Example) was less than 20 minutes in continuous machining. From the above results, it was found that the cutting tools of the examples (sample numbers 1 to 8) had excellent crater wear resistance.

  As described above, the embodiments and examples of the present invention have been described. However, it is originally planned to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed this time are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the embodiments and examples described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The above description includes the features described below.
(Appendix 1)
The method for manufacturing a cutting tool,
A first step of preparing the base material having the rake face,
A second step of forming a film containing the α-Al ₂ O ₃ layer on the rake face of the substrate by using a chemical vapor deposition method,
A third step of blasting the α-Al ₂ O ₃ layer on the rake face;
And a method for manufacturing a cutting tool.
(Appendix 2)
In the second step, the α-Al ₂ O ₃ layer is formed at a temperature of 1000 ° C. to 1100 ° C. and a pressure of 0.1 hPa to 100 hPa,
The temperature is continuously lowered at a rate of 0.3 ° C./min to 0.5 ° C./min during a time period of 90 minutes to less than 180 minutes at the end of forming the α-Al ₂ O ₃ layer. The method for manufacturing a cutting tool according to claim 1, comprising:

REFERENCE SIGNS LIST 1 rake face, 2 flank face, 3 edge ridge, 10 base material, 20 α-Al ₂ O ₃ layer, 21 (001) -oriented crystal grains, 22 crystal grains other than (001) -oriented crystal grains, 30 CVD Apparatus, 31 substrate setting jig, 32 reaction vessel, 33 temperature controller, 34 gas inlet, 35 gas inlet pipe, 36 through hole, 40 coating, 50 cutting tool, D1 virtual plane D1, D2 virtual plane D2, P1a 1a area, P2a 2a area, P3a minimum point, P1b 1b area, P2b 2b area, P3b minimum point, r1 area r1.

Claims (5)

A cutting tool comprising a substrate having a rake face and a coating covering the rake face,
The coating includes an α-Al ₂ O ₃ layer provided on the substrate,
The α-Al ₂ O ₃ layer includes α-Al ₂ O ₃ crystal grains,
The α-Al ₂ O ₃ layer has an area ratio of the (001) -oriented crystal grains in the rake face of 50% or more and 90% or less,
In the measurement of residual stress by 2θ-sin ² ψ method using X-ray,
The residual stress A _A in the film determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −1000 MPa or more and less than 0 MPa,
The residual stress B _A in the film determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake face is −1000 MPa or more and less than 0 MPa,
A cutting tool that satisfies the relational expression | A _A | ≦ | B _A |. The thickness of the α-Al ₂ O ₃ layer is 1 μm or more and 20 μm or less;
From the α-Al ₂ O ₃ on the opposite side to the substrate in layers surface, a virtual plane located at a distance d ₁₀ of 10% of the thickness of the α-Al ₂ O ₃ layer toward the substrate side D1,
An imaginary plane located at a distance d ₄₀ of 40% of the thickness of the α-Al ₂ O ₃ layer from the surface of the α-Al ₂ O ₃ layer opposite to the base material toward the base material side D2,
In the residual stress measurement by the constant penetration depth method using X-rays in the region r1 sandwiched between
Residual stress A determined based on the crystal plane spacing of the (001) plane of the α-Al ₂ O ₃ layer on the rake plane is −800 MPa or more and 600 MPa or less,
The residual stress B determined based on the crystal plane spacing of the (110) plane of the α-Al ₂ O ₃ layer on the rake plane is −1300 MPa or more and 400 MPa or less,
The cutting tool according to claim 1, which satisfies a relational expression of A> B. The stress distribution of the residual stress A is:
From the surface of the α-Al ₂ O ₃ layer opposite to the substrate toward the substrate, a 1a region in which the residual stress A continuously decreases,
A second a region in which the residual stress A continuously increases from the surface opposite to the substrate and from the surface opposite to the substrate toward the substrate. And
The cutting tool according to claim 1, wherein the first a region and the second a region are continuous via a minimum point of the residual stress A. 4. The stress distribution of the residual stress B is:
A first b region in which the residual stress B continuously decreases from the surface of the α-Al ₂ O ₃ layer opposite to the base toward the base;
A second b region in which the residual stress B continuously increases from a surface opposite to the substrate and from the surface opposite to the substrate toward the substrate. And
The cutting tool according to claim 2 or 3, wherein the first region (b) and the second region (b) are continuous via a minimum point of the residual stress B. The coating further includes one or more intermediate layers provided between the substrate and the α-Al ₂ O ₃ layer,
The intermediate layer includes at least one element selected from the group consisting of a group 4 element, a group 5 element, a group 6 element, Al and Si, and at least one element selected from the group consisting of C, N, B and O. The cutting tool according to any one of claims 1 to 4, wherein the cutting tool includes a compound consisting of a kind of element.

Images